Mechanisms displaying a time indication, such as the date, are known to those skilled in the art. They typically include a display member, such as a date ring, a mechanism driving the display member, and a correction device activated by a winding stem. Correction devices are generally complex and cumbersome. They typically include at least one intermediate wheel activated by a pinion mounted on the winding stem, and a sliding or stationary corrector pinion, meshed with the intermediate wheel and with the display member.
A major drawback of this type of correction device is its thickness, mainly due to the intermediate wheel, which includes two toothing levels. By way of example, JP Patent No 59 160791 may be cited, wherein the intermediate wheel includes a first toothing level meshed with the pinion of the winding stem, and a second toothing level meshed with a second intermediate wheel. In JP Patent No 48 35856, the intermediate wheel is arranged as an overthickness of the winding stem pinion. It includes a contrate toothing meshed with the pinion, and a radial toothing meshed with the corrector pinion. Further, the corrector pinion also includes two active levels. Because of their thickness, these devices are not suited to ultra-thin movements.
Other correction devices, of much simpler design, include a pinion mounted on the winding stem, directly meshed with a toothing of the display member. The pinion therefore includes two substantially helical wings, arranged for cooperating in one direction of rotation only, with the toothing of the display member. The display member is generally positioned using a jumper spring. This type of correction device is certainly extremely simple, but it is cumbersome for display members of large diameter Indeed, the diameter of the pinion must be in ratio to the pitch of the display member toothing, so that each wing drives the display member through one step when the pinion rotates. The diameter of the pinion is, consequently, all the more important the larger the diameter of the display member, which is why this device is ill suited to ultra-thin movements.